(a) Field of the Invention
The present invention relates to a chemical vapor deposition apparatus.
(b) Description of the Related Art
Chemical vapor deposition (CVD) forms a thin film on a substrate by the reaction of vapor phase chemicals (reactants) that contain the required constituents. The reactant gases are introduced into a reaction chamber and decomposed and reacted at a heated surface of the substrate to form the thin film. A wide variety of thin films utilized in a manufacturing process of a semiconductor device such as a thin film transistor (TFT) liquid crystal display (LCD) is prepared by CVD.
A CVD system includes a diffuser for evenly distributing the reactant gases over a substrate. The diffuser is made of metal to serve as a powered electrode, and it is combined with a diffuser frame serving as an electrode extension by bolts. Since there is a gap between the diffuser and the diffuser frame, an arc may be generated in the gate when the diffuser 70 is supplied with high radio frequency power. The arc may remove oxide such as Al2O3 coated on the diffuser and the diffuser frame, and the metal forming the diffuser may melt and drop onto the substrate. The dropped metal component generates splash defects to reduce the quality of deposited thin films.
In addition, since the bolts for combining the diffuser and the diffuser frame make gaps with the diffuser and the diffuser frame, arc generation may be also made in the gaps. Accordingly, several particles are separated from the bolts to cause defects.